1. Field of the Invention
The present invention relates to a liquid discharge head for discharging liquid and a method for manufacturing the same.
2. Description of the Related Art
Recently, an ink jet head comes into existence as a liquid discharge head in widespread use. In these years, an ink jet recording apparatus having this ink jet head mounted thereon has largely decreased in price, and therefore a challenge arises how to manufacture the ink jet head in a low cost. For that purpose, miniaturization of a liquid discharge substrate especially has a useful role. For example, because the miniaturization of the liquid discharge substrate allows more liquid discharge substrates to be cut out from a silicon wafer, costs of the ink jet head, i.e., the liquid discharge head, can be reduced.
However, the more the liquid discharge substrate is miniaturized, the smaller a size or pitch of a joint portion of an electrode lead terminal for supplying power and a drive signal becomes, so that it is more difficult to ensure joint reliability. Therefore, it becomes difficult to form, on a surface of a head substrate, an electrical connecting portion to which the electrode lead terminal for supplying power and a drive signal is connected, in a manner that the electrical connecting portion is formed on a conventional head substrate.
Japanese Patent Application Laid-Open No. H11-192705 discloses, as a conventional example for solving the problem of electrical connectivity concerning the ink jet head, a print head having an electrical connection electrode on a surface of a silicon substrate opposing to a surface on which a discharge port is disposed.
FIG. 9 is a partial cross-section view illustrating an electrical connection configuration of the print head disclosed in Japanese Patent Application Laid-Open No. H11-192705 and including the print head and a support substrate.
Referring to FIG. 9, a plurality of print heads 218 is mounted on a support substrate 220.
Each of the plurality of print heads 218 has an electrode 284 for electrical connection and an ink supply port 242 formed on a back surface thereof opposing to a surface on which a nozzle opening 238 is formed. A support substrate 220 for holding the print head 218 has electrical wiring applied on a first surface 270 and a second surface 272. Then, on the first surface 270, the print head 218 is electrically connected using a solder bump and mounted. Further, a logic circuit (not shown) and a drive circuit 230 are mounted on the second surface 272 of the support substrate 220 opposing to the first surface.
However, the ink jet head disclosed in Japanese Patent Application Laid-Open No. H11-192705 has the following problems.
There is a problem relating to sealing of an electrical connecting portion (reliability of quality). The ink jet head is mounted and operated on the ink jet recording apparatus, and used in a state at all times exposed to the environment of ink. Japanese Patent Application Laid-Open No. H11-192705 especially does not describe, in detail, sealing at a joint portion between the electrode on the back surface of the print head and the electrical wiring on a front surface of the support substrate. Therefore, measures are not known against troubles caused by absolutely unanticipated phenomena, such as electrical troubles always due to ink (for example, short circuit and open circuit), and chemical troubles (for example, corrosion or elution of an element (material) used, and change in characteristics of ink components).
Further, a semiconductor element or the like, generally, is completely enclosed with resin such as epoxy to be packaged and completely hermetically sealed without a pin hole, a gap and the like, from the viewpoint of reliability. Similarly to this, the liquid discharge head also is processed, and, needless to say concerning the electrode described above, also a gap between a substrate having a semiconductor element mounted thereon, such as a liquid discharge substrate, and a support member for supporting this substrate has to be completely hermetically sealed.
Further, in the case of sealing at the liquid discharge head, in order to secure liquid discharge performance and landing accuracy in an impact area where discharged liquid impacts a medium, it is necessary to prevent sealing resin from impairing normal functions of the discharge port and a liquid supply port. Therefore, there is restriction specific to the liquid discharge head and severer than that required for a usual semiconductor element, relating to the sealing.